Friday, July 30, 1999 Published at 06:27 GMT 07:27 UKSci/TechMade-to-measure transplant breakthroughHuman embryonic stem cells could be the key to a medical revolutionThe best evidence yet that new human tissue or organs could one day be grown in the laboratory and successfully implanted has come from a study on rats.

The scientists, led by Oliver Brustle, at the University of Bonn Medical Centre, repaired the damaged nervous systems of rats using cells taken from embryos.

The embryonic stem cells that the researchers used have the ability to develop into every kind of tissue in the body from blood to bone to muscle.

Transplant transformation

Medical researchers are increasingly excited that if these cells can be multiplied in the laboratory and then coaxed with chemicals into developing into the desired tissue type, then an unlimited supply of transplant material will become available.

Stem cells can now be cultured in the lab

Furthermore, if cloning techniques were also used, the tissue would be a perfect match for the patient, abolishing any concerns about transplant rejection.

However, to make progress on the application of this technology to humans, scientists need to work with human embryos. In June, the UK government rejected expert advice to relax its rules on this type of research. In the US, the National Bioethics Advisory Committee has recommended the US government lift its restrictions on human embryonic stem cells, but it has not yet done so.

There has been prominent opposition to making it any easier to do these experiments from religious and pro-life groups.

Nerve experiments

Professor Brustle's team succeeded in growing embryonic stem cells from rats in the laboratory and then coaxing them with growth factor chemicals to form into key elements of the central nervous system.

Two kinds of cell were produced which, when transplanted into rats born with damaged nerves, swiftly began to carry out repairs.

The rats lacked myelin, the fatty sheath that protects and insulates nerves. Without myelin, nerve fibres conduct electrical impulses slowly or not at all.

A loss of myelin is seen in a number of serious genetic and acquired neurological diseases, the best known being multiple sclerosis.

Eventual applications

The research is published in the journal Science and Professor Brustle said: "Our experiments are a first example of an application of this stem cell technique to a neurological disorder."

"Our findings demonstrate that cells that have never seen a brain can be developed into specific donor cells for nervous system repair," he added.

Co-researcher Ian Duncan, at the University of Wisconsin-Madison, said: "We believe eventually it will have clinical applications."

Dr Lorna Layward, head of research at the MS Society, said: "Multiple Sclerosis is caused by an on-going autoimmune attack on myelin. The idea of transplanting cells that can make new myelin is a potential therapy, but at the moment it's still in the laboratory."